medium CVSS 5.5

CVE-2024-36966·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: erofs: reliably distinguish block based and fscache mode When erofs_kill_sb() is called in block dev based mode, s_bdev may not have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will be mistaken for fscache mode, and then attempt to free an anon_dev that has never been allocated, triggering the following warning: ============================================ ida_free called for id=0 which is not allocated. WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140 Modules linked in: CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630 RIP: 0010:ida_free+0x134/0x140 Call Trace: <TASK> erofs_kill_sb+0x81/0x90 deactivate_locked_super+0x35/0x80 get_tree_bdev+0x136/0x1e0 vfs_get_tree+0x2c/0xf0 do_new_mount+0x190/0x2f0 [...] ============================================ Now when erofs_kill_sb() is called, erofs_sb_info must have been initialised, so use sbi->fsid to distinguish between the two modes.

Severity
medium
Software
Kernel
Fixed in
6.8.11
Published
2024-06-08

Affected versions

From: 6.7

Until: 6.8.11

Fixed in: 6.8.11

How to fix this CVE

Update your Linux kernel to version 6.8.11 or later to resolve a resource management flaw in EROFS filesystem handling. This vulnerability affects systems with CONFIG_EROFS_FS_ONDEMAND enabled, causing kernel warnings and potential instability during mount operations. Apply the latest kernel patches from your distribution's stable repository.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your kernel version with 'uname -r' and compare against 6.8.11 — versions 6.7.x through 6.8.10 are vulnerable
  2. Step 2: Verify if EROFS filesystem is in use by checking 'mount | grep erofs' and 'grep CONFIG_EROFS_FS_ONDEMAND /boot/config-$(uname -r)'
  3. Step 3: Search kernel logs for 'ida_free called for id=0 which is not allocated' warnings using 'dmesg | grep ida_free' or 'journalctl -xe | grep ida_free'
  4. Step 4: After patching, run 'uname -r' to confirm the updated kernel version is active (may require reboot) and remount EROFS filesystems to verify stability

FAQ

What is CVE-2024-36966?

This vulnerability exists in the Linux kernel's EROFS filesystem implementation where the shutdown routine (erofs_kill_sb) incorrectly distinguishes between block-device and fscache modes when CONFIG_EROFS_FS_ONDEMAND is enabled, leading to attempts to free unallocated device IDs and generating kernel warnings.

Is CVE-2024-36966 being actively exploited?

No — this CVE is not listed on CISA's Known Exploited Vulnerabilities catalog and no public exploits are available. However, it can cause system instability and kernel warnings during normal EROFS mount operations.

What versions of Kernel are affected by CVE-2024-36966?

Linux kernel versions 6.7.0 through 6.8.10 are affected. Version 6.8.11 and later contain the fix. Systems running kernels outside this range are not vulnerable.

How do I check if my server is vulnerable to CVE-2024-36966?

Run 'uname -r' and verify the version is between 6.7 and 6.8.10. Then check 'grep CONFIG_EROFS_FS_ONDEMAND /boot/config-$(uname -r)' — if it shows 'y', your system is vulnerable only if using EROFS filesystems.

Does Defensia detect CVE-2024-36966?

Yes — Defensia's CVE advisory scanner compares installed kernel versions against the NVD database. If a vulnerable kernel version is detected on a monitored server, CVE-2024-36966 will appear in your dashboard with automated remediation guidance and patch availability.

Related Kernel CVEs

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CVE-2026-64439CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: crypto: krb5 - filter out async aead implementations at alloc krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL completion callback and treat any negative return from crypto_aead_{encrypt,decrypt}() as terminal, falling through to kfree_sensitive(buffer). When the encrypt_name resolves to an async AEAD instance the request returns -EINPROGRESS, the buffer is freed while the backend's worker still holds a pointer, and the worker dereferences the freed slab on completion. KASAN report under UML+SLUB with a synthetic async aead backend bound to krb5->encrypt_name: BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7 The helpers were written synchronously, so filter the async instances out at allocation time instead of plumbing crypto_wait_req() through every call site. Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems with an async AEAD provider bound to the krb5 enctype name.
CVE-2026-64066CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfs_read_to_pagecache() to pause on subreq failure Fix netfs_read_to_pagecache() so that it pauses the generation of new subrequests if an already-issued subrequest fails.
CVE-2026-64383CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: fix double-free in SMB2_flush() replay SMB2_flush() keeps its response buffer bookkeeping across replay attempts. If a replayable flush response is received and the retry then fails before cifs_send_recv() stores a replacement response, flush_exit will free the stale response pointer a second time. Reinitialize resp_buftype and rsp_iov at the top of the replay loop so cleanup only acts on response state produced by the current attempt. This fixes a double-free without changing replay handling for successful requests.
CVE-2026-64067CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix missing barriers when accessing stream->subrequests locklessly The list of subrequests attached to stream->subrequests is accessed without locks by netfs_collect_read_results() and netfs_collect_write_results(), and then they access subreq->flags without taking a barrier after getting the subreq pointer from the list. Relatedly, the functions that build the list don't use any sort of write barrier when constructing the list to make sure that the NETFS_SREQ_IN_PROGRESS flag is perceived to be set first if no lock is taken. Fix this by: (1) Add a new list_add_tail_release() function that uses a release barrier to set the pointer to the new member of the list. (2) Add a new list_first_entry_or_null_acquire() function that uses an acquire barrier to read the pointer to the first member in a list (or return NULL). (3) Use list_add_tail_release() when adding a subreq to ->subrequests. (4) Use list_first_entry_or_null_acquire() when initially accessing the front of the list (when an item is removed, the pointer to the new front iterm is obtained under the same lock).

References

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